diff --git a/test-suite/tests/c-api.test b/test-suite/tests/c-api.test
index 06dba53c5..6d6f91f85 100644
--- a/test-suite/tests/c-api.test
+++ b/test-suite/tests/c-api.test
@@ -22,7 +22,7 @@
 (define srcdir (cdr (assq 'srcdir %guile-build-info)))
 
 (define (egrep string filename)
-  (zero? (system (string-append "grep -E '" string "' " filename
+  (zero? (system (string-append "grep -E \"" string "\" " filename
                                 " >" %null-device))))
 
 (define (seek-offset-test dirname)